Mobile communication terminal and electro-acoustic transducer used for the same

ABSTRACT

A portable communication terminal employs an electro-acoustic transducer having openings on the housing. The openings of the transducer are coupled to a housing of the terminal or acoustic pipes unitarily formed with the housing of the transducer. An opening of the acoustic pipe faces an opening provided in the housing of the terminal. The terminal uses a transducer including a diaphragm, a cover closely jointed to an outer periphery of the diaphragm and facing a front face of the diaphragm, and a frame provided at a rear face of the diaphragm. The terminal and the transducer consume less power and yet radiate greater output sound pressure with smaller bodies. They can deliver sound from a display section, so that a user accepts the sound normally.

TECHNICAL FIELD

The present invention relates to portable communication terminals suchas a portable telephone, a personal handy-phone system (PHS), or aportable computer employing a communication modem therein. The presentinvention also relates to an electro-acoustic transducer (hereinafterreferred to as a transducer) to be used in the same portablecommunication terminals.

BACKGROUND ART

A conventional portable communication terminal is described withreference to FIGS. 11 (a), 11 (b), 11 (c) and FIG. 12 which illustrate aportable telephone. FIG. 11( a) is a front view of the portabletelephone in use. FIG. 11( b) is a side view of the same including apartial sectional view. FIG. 11( c) is a rear view of the same. FIG. 12is a side sectional view of a transducer incorporated in the portabletelephone.

In FIG. 11( a), on the front face of portable telephone 10, operatingsection 10 a including pushbutton digits is prepared, and a transmitter(not shown) is also provided to the front face. Display section 10 bincluding a liquid crystal display is disposed on an upper part of thefront face, and a receiver (not shown) is provided to this upper part.In FIG. 11( c), opening 10 c is provided on the rear face and guides thesound generated by transducer 11 to the outside.

A structure of transducer 11 is described with reference to FIG. 12.Circular diaphragm 1 generating aerial vibration is supported by frame 2at its outer periphery with adhesive. Frame 2 includes a plurality offirst sound-paths 2 a. An end of voice coil 3 is rigidly fixed to acenter portion of diaphragm 1, and both the ends of voice coil 3 areelectrically coupled to terminal section 4 disposed at a lower endportion of frame 2.

A magnetic circuit formed of magnet 5, top plate 6 and yoke 7 isdisposed in a recess provided at a center of frame 2. Voice coil 3 isinserted in a space (magnetic gap) between the outer periphery of topplate 6 and the inner wall of yoke 7.

Protector 8, to which second sound-paths 8 a are provided, protectsdiaphragm 1, and forms a housing of the transducer together with frame2. The foregoing portable telephone thus radiates only the sounddelivered from second sound-paths 8 a provided to protector 8 to theoutside. On the other hand, the sound delivered from first sound-paths 2a provided to frame 2 is radiated within portable telephone 10. For thatpurpose, protector 8 is bonded to the inner wall of phone 10 via aspacer, so that transducer 11 is mounted in phone 10. This structureallows the sound delivered from first sound-paths 2 a and the sound fromsecond sound-paths 8 a of protector 8 to be separated and free frominterference.

The portable telephone has changed its function drastically from atelephone to an information terminal these days. This change entails thefollowing requirements from the market: more sophisticated performancesof the display such as a larger and color display, and bettercharacteristics on an output sound-pressure from the display side as aninteractive device. Further, a display of portable communicationterminals such as portable telephones accompanies sound more often, suchas reproduced sound of a video game, or a tone verifying a operation ofpushed buttons.

Under these circumstances, reproduced sound by a conventional transduceror a conventional mounting structure of the transducer in operating thedisplay lowers a directivity toward the front side of the communicationterminal due to diffraction effect, because the sound is delivered onlyfrom second sound-paths 8 a. Thus, sufficient volume and quality ofsound cannot be expected to the front side of the portable telephone.The present invention aims to provide a portable communication terminalthat overcomes the foregoing problems.

SUMMARY OF THE INVENTION

A portable communication terminal of the present invention uses atransducer having an opening formed on a housing thereof. The opening ofthe transducer is coupled to an acoustic pipe unitarily formed (i.e.,formed as one piece) with the housing of the communication terminal orthe housing of the transducer. An opening of the acoustic pipe faces anopening provided in the housing of the communication terminal. Theportable communication terminal of the present invention includes acover and a frame, which are brought into close contact with the outerperiphery of a diaphragm, on a front face and a rear face of thediaphragm, respectively. The terminal uses a transducer including atleast two openings on the cover and the frame. A transducer used in anembodiment of the present invention has at least two conduits, such asopenings or acoustic pipes, on either one of the frame or the cover. Atransducer used in another embodiment of the present invention includesat least one conduit, such as the opening or the acoustic pipe, on theframe and includes the remaining conduit on the cover. The areas ofrespective openings provided to the cover and the frame areapproximately equal to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a front view of a portable telephone in use as anembodiment of a portable communication terminal of the presentinvention.

FIG. 1( b) is a partially sectional side view of the portable telephoneshown in FIG. 1( a).

FIG. 1( c) is a rear view of the same portable telephone.

FIG. 2 is a side sectional view of a transducer to be used in theportable telephone shown in FIGS. 1( a)–1(c).

FIG. 3 is an exploded perspective view of the transducer.

FIG. 4( a) is a side sectional view of a transducer in accordance with asecond exemplary embodiment of the present invention.

FIG. 4( b) is a perspective bottom view of the transducer in accordancewith the second exemplary embodiment of the present invention.

FIG. 5( a) is a perspective view of a portable telephone in accordancewith the second exemplary embodiment of the present invention.

FIG. 5( b) is a perspective rear view of the same portable telephone.

FIG. 5( c) is a front view illustrating a folded status of the portabletelephone.

FIG. 6( a) is a perspective view of a modification of the secondexemplary embodiment of the present invention.

FIG. 6( b) is a perspective rear view of the modification.

FIG. 7( a) is a perspective view of another modification.

FIG. 7( b) is a perspective rear view of the same.

FIG. 7( c) is a sectional view of an essential part of the same.

FIG. 8 is a perspective view of still another modification.

FIG. 9( a) is a perspective view of yet another modification.

FIG. 9( b) is a perspective rear view of the same.

FIG. 10 is a graph illustrating the characteristics of sound pressurelevel vs. frequency of the modification shown in FIG. 9.

FIG. 11( a) is a front view of a conventional portable telephone in use.

FIG. 11( b) is a side view with a half sectional view of theconventional portable telephone.

FIG. 11( c) is a rear view of the same.

FIG. 12 is a side sectional view of a conventional transducer used inthe conventional portable telephone.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention is described using a portabletelephone as an example with reference to the accompanying drawings.Similar elements to those described in the background art have the samereference marks, and the descriptions thereof are omitted here.

First Exemplary Embodiment

FIG. 1( a) is a front view of a portable telephone in use as anembodiment of a portable communication terminal of the presentinvention. FIG. 1( b) is a partially sectional side view of the same.FIG. 1( c) is a rear view of the same. FIG. 2 is a side sectional viewof a transducer incorporated in the portable telephone shown in FIGS. 1(a)–1(c). FIG. 3 shows a perspective exploded view of the transducer.

In FIG. 1( a) through FIG. 3, first opening 10 d is provided in displaysection 10 b of portable telephone 12, and second opening 10 e isprovided in a rear side of display section 10 b. Transducer 13 built inportable telephone 12 includes second acoustic pipe 13 b, which deliverssound from transducer 13 through first opening 10 d, and first acousticpipe 13 a, which also delivers sound from transducer 13 through secondopening 10 e.

In the present embodiment, as shown in FIG. 3, first acoustic pipe 13 ais unitarily molded (i.e., molded as one piece) with protector (cover) 8b which covers a diaphragm, when protector 8 b is molded of resin.Second acoustic pipe 13 b is unitarily molded (i.e., molded as onepiece) with frame 2 b when frame 2 b is resin molded.

The acoustic pipes are not necessarily molded with protector 8 b andframe 2 b simultaneously. However, molding at the same time results inlowering the cost. Acoustic pipe sections can be molded at a time whenthe housing of phone 12 is molded, and the openings are provided to thefirst and second acoustic pipe sections of transducer 13.

As shown in FIG. 12, conventional transducer 11 has sound-paths 2 a inframe 2. However, since a magnetic circuit is mounted to frame 2, thereis not enough space for sound-paths 2 a. As a result, sound-paths 2 aonly have minimal opening areas so as not to restrict diaphragm 1 fromvibrating, and to decrease the sound radiation from sound-paths 8 a ofprotector 8. In the present embodiment, on the other hand, an openingarea of first acoustic pipe 13 a and an opening area of second acousticpipe 13 b are nearly equal, so that an audible difference detected byusers can be suppressed. Further, since there are no restrictions suchas in the conventional transducer, acoustic pipes 13 a and 13 b can havelarger opening areas and can radiate the sound from transducer 13 to theoutside efficiently. As a result, a greater sound volume can beexpected.

First acoustic pipe 13 a and second acoustic pipe 13 b are placedsymmetrically with respect to diaphragm 1, so that diaphragm 1 isprevented from rolling when it is driven.

Transducer 13 structured as described above radiates respective soundsfrom first opening 10 d and second opening 10 e with 180 degrees phasedifference (anti-phase). In other words, this is because acoustic pipes13 a and 13 b are provided, respectively, to the front face and the rearface of diaphragm 1. Therefore, around the side faces of the portabletelephone, where the sounds from both of the acoustic pipes diffuse andclash with each other, the sounds radiated interfere with each other andattenuate to suppress sounds. On the other hand, in front of theportable telephone, where a user actually needs the sound, efficientlyloud sound can be heard.

When portable telephone 12 is folded and carried in a user's pocket,second acoustic pipe 13 b is covered by operating section 10 a. Thus,the sound radiated from first acoustic pipe 13 a open to the rear faceperforms paging. In this case, an efficiently loud sound can also beheard similar to the sound from the front face.

As discussed above, the portable communication terminal of the presentinvention radiates loud sound in a direction where the sound is needed,and restricts sound radiation along side faces of a portable telephonewhere essentially the sound is not needed.

In the present embodiment, a single transducer 13 radiates the soundthrough first acoustic pipe 13 a and second acoustic pipe 13 b, thenfrom both of the front and rear faces of portable telephone 12. Thisstructure thus can downsize portable telephone 12. To be more specific,when conventional portable telephone 10 radiates sound from both of thefront face and the rear face (i.e., either of the main faces), and yetit restricts the sound from radiating in other directions (namely, whenthe conventional phone aims only to improve directivity from the frontand rear faces), different transducers are independently used forradiating the sound from the front face and the rear face (the mainfaces). In this case, sound signals supplied to the respectivetransducers have 180 degrees phase-difference from each other. In fact,this structure can achieve the present objective. However, theconventional phone needs two transducers, makes the circuit complicatedand requires more power, i.e., a larger battery. The present embodimentcan overcome those problems.

Transducer 13 used in the present embodiment has first acoustic pipe 13a on protector 8 b which works as a part of the housing of transducer13, and second acoustic pipe 13 b on frame 2 b which is another part ofthe housing. However, if a space for mounting the transducer to theportable telephone 12 is limited, alternate forms of conduits can beused. For example, conduits such as only openings instead of pipes canwork well enough. Whether or not to employ the acoustic pipes or use apipe on only either side can be determined accordingly.

The portable communication terminal in accordance with the presentembodiment radiates sounds from both its front and rear faces to achieveexcellent directivity. On the other hand, in other surrounding areas ofthe terminal, the sounds from the front and rear faces cancel each otherbecause they have 180 degrees phase difference, so that the terminal caninhibit the sound radiation from adversely affecting the surroundings.

Second Exemplary Embodiment

FIG. 4( a) is a side sectional view of a transducer in accordance withthe second exemplary embodiment of the present invention. FIG. 4( b) isa perspective bottom view of the transducer. The second embodimentdiffers from the first one in the following points: First acoustic pipe32 b and second acoustic pipe 32 c are unitarily formed (i.e., formed asone piece) with resin frame 32 a in which a magnetic circuit isinsert-molded. Both of the acoustic pipes are provided under diaphragm33, so that the sound waves produced and radiated by the vibration ofdiaphragm 33 passing through tubes 32 b and 32 c are in-phase. Firstacoustic pipe 32 b radiates the sound downward, and second acoustic pipe32 c radiates the sound in a side direction. Acoustic pipes 32 b and 32c thus radiate the sound in two directions different from each other by90 degrees. Since the sound waves radiated are in-phase, they do notinterfere with each other and the sound pressure level can be increased.

Third Exemplary Embodiment

FIGS. 5( a) and 5(b) are perspective views of a folding type portabletelephone using a transducer in accordance with the second exemplaryembodiment of the present invention. FIG. 5( c) is a front viewillustrating a folded status of the portable telephone in a user'spocket. Portable telephone 40 includes display section 41 for displayinginput information and information obtained through a telephonecommunication, and operating section 42 through which a telephone numberor the like is entered.

First opening 43 placed at a lower section of display section 41 iscoupled to first acoustic pipe 32 b of the transducer described in thesecond embodiment. Second opening 44 provided on a lower end face ofdisplay section 41 is coupled to second acoustic pipe 32 c of thetransducer.

Those connections between the first and second acoustic pipes of thetransducer and the first and second openings of the portable telephoneremain the same in the following embodiments and modifications, and thedescriptions thereof are omitted hereinafter.

Since second opening 44 is provided at an end face of the portabletelephone, a paging tone can be radiated from this end face when thephone is kept in the user's breast pocket as shown in FIG. 2( c). Theuser thus can notice a call with ease.

In the present embodiment, second opening 44 is provided at the lowerend face. However, the opening can be provided at a side face. Accordingto the present embodiment, there are less obstacles between the phoneand the user's ear when the phone is kept in user's pocket as comparedwith the conventional portable telephone that has a sound radiating pathof a transducer in the rear face of the phone. A user thus can notice apaging tone with ease. A situated status of the portable telephone inthe user's pocket proposes that the second opening be provided at anupper end or a lower end of a rectangular portable telephone so thatless obstacles between the phone and the user's ear can be expected.

In the present embodiment, when the portable telephone is folded over,first opening 43 provided at display section 41 is closed when a pagingtone is delivered. Thus the sound pressure from second opening 44increases, and a more remarkable paging tone can be delivered to a user.When a user opens the portable telephone for use, second opening 44 isclosed with an end face of operating section 42, so that a soundpressure from first opening 43 can be increased.

Placement of the opening shown in FIG. 5( a) allows a user to accept theinformation displayed on display section 41 and the loud sound fromopening 43 quite normally because both forms of information come fromthe same direction. The paging tone and the loud sound can be radiatedby a single transducer, so that the transducer occupies a smaller spaceand contributes to downsizing the portable telephone.

FIG. 6( a) through FIG. 9( b) show examples modified from the presentembodiment. Each one of the examples includes first openings 45, 47, 49or 51 that delivers sound upward when the phone is in use, and secondopenings 46, 48, 50 or 52 that delivers sound from any one of an upperend face, a lower end face, and a side face when the phone is folded.This placement of the openings allows a user to notice a paging tonewith ease when the phone is folded over. The arrangement also allows auser to accept sound normally from the first opening because the userhears the sound as if it comes from an operating section or a displaytoward the user.

Further, those examples use the transducer in accordance with the secondembodiment, namely, first acoustic pipe 32 b is coupled to the firstopening and second acoustic pipe 32 c is coupled to the second opening.This single transducer thus can deliver the sound in two directions, andcontributes to downsizing the portable telephone.

FIGS. 6( a) and 6(b) show a folding type portable telephone in whichfirst opening 45 is provided at an upper part of operating section 42and second opening 46 is provided at an upper end face of operatingsection 42. When the phone is folded, first opening 45 is closed withoperating section 42, so that a sound pressure of a paging tonedelivered from second opening 46 is increased. Further, when the phoneis in use, second opening 46 is closed with a lower end face of displaysection 41, so that a sound pressure of sound radiated from firstopening 45 is increased.

FIGS. 7( a) and 7(b) show a folding type portable telephone whichincludes first opening 47 on an upper section of display 41 and secondopening 48 on a side face at an upper section. When the phone is folded,first opening 47 is closed by operating section 42, so that a soundpressure of a paging tone delivered from second opening 48 is increased.When the phone is in use, since the radiated sounds are in-phase, anoutput from second opening 48 passes in front of display 41, whichvirtually results in increasing the output sound pressure of firstopening 47.

FIGS. 7( a) and 7(b) show the folding type portable telephone. However,as shown in FIG. 7( c), a straight (not folding) portable telephone canhave first opening 47 on an upper section of a display section andsecond opening 48 on a side face at a upper section or on an upper endface. This structure allows a single transducer to deliver a paging tonewhen the phone is kept in a user's pocket, and to radiate sound from afront face (i.e., a face where the display section is located), so thatthe portable telephone can be downsized. Similar to the modified exampleshown in FIGS. 7( a) and 7(b), the outputs from the first and the secondopenings are in-phase, so that a sound pressure of the output canincrease. In the straight portable telephone, the first opening may beprovided at a lower face of the operating section and the second openingcan be provided at a lower side face or a lower end face. This structureproduces the same advantage as what is discussed above.

FIG. 8 shows a folding type portable telephone which has a first opening49 at a lower part of operating section 42 and second opening 50 on alower end face of operating section 42. When the phone is folded, firstopening 49 is closed by display section 41, so that a sound pressure ofa paging tone delivered from second opening 50 increases. Further, whenthe phone is in use, an output from second opening 50 passes in front ofdisplay 41, which virtually results in increasing the sound pressure ofan output from first opening 49.

FIGS. 9( a) and 9(b) show a folding portable telephone which has a firstopening 51 at an upper part of operating section 42 and second opening52 on a side face of operating section 42 at an upper part. When thephone is folded, first opening 51 is closed with display section 41 sothat a sound pressure of a paging tone delivered from second opening 52increases. Since sounds radiated when the phone is in use are in-phase,an output from second opening 52 passes in front of operating section42, which virtually results in increasing the sound pressure of outputfrom first opening 51.

FIG. 10 is a graph illustrating sound pressure level vs. frequencycharacteristics at display section 41. Curve X indicates thecharacteristics of the portable telephone shown in FIG. 5( a) in use.Second opening 44 is closed with the end face of operating section 42.Curve Y indicates the characteristics of the portable telephone shown inFIG. 7( a), and curve Z indicates the characteristics of a conventionalportable telephone.

As FIG. 10 shows, it is confirmed that a structure having an openingdisposed on a display section and another opening, with its open areaclosed, disposed on a side face when a phone is in use, radiates thehighest sound pressure output. A structure having an opening on a sideface and an output therefrom passing in front of a display, is next tothe foregoing structure and better than the conventional one.

As discussed above, a plurality of acoustic pipes are formed in a frameof a transducer, and the acoustic pipes are provided on the same side ofa diaphragm of the transducer. A use of this transducer in a portabletelephone can increase an output sound pressure and downsize theportable telephone.

In the first through third embodiments, two acoustic pipes and twoopenings are used as examples. However, the number of acoustic pipes andopenings of a communication terminal can be three or more depending onacoustic characteristics and other requirements. Then variousmodification can be developed, such as sound can be radiated from anoperating section and both sides simultaneously.

Further in the previous descriptions, a dynamic transducer is used.However, not to mention, the present invention is not limited to thedynamic transducer, and it is applicable to a piezoelectric transducer.The piezoelectric transducer includes two types, one is to drive apiezoelectric ceramic member or a piezoelectric film directly with anelectric signal, thereby producing sound, and the other one is to couplea piezoelectric ceramic member to a diaphragm for producing sound. Adiaphragm using a piezoelectric film or a diaphragm coupled to apiezoelectric ceramic is fit to the present invention among others. Ause of such a piezoelectric transducer advantageously decreases powerconsumption of the portable telephone.

INDUSTRIAL APPLICABILITY

A portable communication terminal and an electro-acoustic transducer tobe used in the terminal of the present invention consumes less power,and yet radiates a greater output sound pressure with smaller bodies.The terminal in use delivers sound which virtually comes from a displaysection so that a user can accept the sound normally. A use of theportable communication terminal and its transducer thus produces greatindustrial advantage.

1. A foldable portable communication terminal comprising: a housinghaving at least two openings; and an electro-acoustic transducer havingat least two conduits, said at least two conduits comprising at leasttwo openings or at least two acoustic pipes, said transducer beingaccommodated in said housing such that each of said conduits faces arespective one of said openings of said housing; wherein at least one ofsaid openings of said housing is arranged so as to be outwardly openwhen said portable communication terminal is folded and so as to beclosed when said portable communication terminal is unfolded for use. 2.A foldable portable communication terminal comprising: a housingincluding a display section and an operating section, said housinghaving at least two openings; and an electro-acoustic transduceraccommodated in said housing, said transducer having at least twoconduits arranged to radiate sound waves having the same phase, said atleast two conduits comprising at least two openings or at least twoacoustic pipes; wherein a first one of said openings of said housing islocated on a main face of one of said display section and said operatingsection, and a second one of said openings of said housing is located ona side face adjacent to said main face of said one of said displaysection and said operating section; and wherein said openings of saidhousing are arranged so that each of said openings of said housing facesa respective one of said conduits of said transducer, and so that atleast one of said openings of said housing is outwardly open when saidportable communication terminal is folded and is closed when saidportable communication terminal is unfolded for use.
 3. Thecommunication terminal of claim 2, wherein said at least two conduits ofsaid transducer comprise at least two openings, said housing having anacoustic pipe unitarily formed therewith and arranged so as to becoupled to at least one of said openings of said transducer.
 4. Thecommunication terminal of claim 2, wherein said at least two conduits ofsaid transducer comprise at least two acoustic pipes arranged such thatan opening of each of said acoustic pipes is coupled to a respective oneof said openings of said housing.
 5. The communication terminal of claim2, wherein said electro-acoustic transducer comprises one of a dynamictransducer and a piezoelectric transducer.
 6. The communication terminalof claim 5, wherein said at least two conduits of said transducercomprise at least two acoustic pipes arranged such that an opening ofeach of said acoustic pipes is coupled to a respective one of saidopenings of said housing.
 7. The communication terminal of claim 2,wherein said transducer includes a frame and a cover joined to an entireperiphery of said frame, said acoustic pipes being connected to one ofsaid frame and said cover.